Both run 24/7 depending on your coal stove. I don't think one would be cheaper to run then the other.

Freddy, Why do say one is more expensive to run?

You could get a power vent/direct vent for you furnace and they would only run when needed (when the furnace is running).

The Direct Vent Mounts "Directly" on the unit and blows the hot exhaust gases out the pipe and the pipe needs to be sealed really good! No baro normally can be installed (no room). Normally sized for the unit.

Power Vent(s) usually mount on the outside of the house and SUCK or PULL the fumes out of the unit, a Baro can be installed and adjusted accordingly, pipes would be under a vacuum (same as using a standard Chimney hookup). Power Vents are usually sized larger for many different operating conditions and sometimes have to be slowed down (via a Rheostat) for some coal applications.

A basic chimney is always the best solution, but if you don't have the room or a good chimney, the power vent is a good alternate.go to http://www.fieldcontrols.com/venting.php for SWG Power Vent information.

A direct vent will require less maintenance because it sits inside your home while a PV will heed the elements outside. A PV will be quieter then a DV. A PV has a baro which helps to save fuel and eliminates the potential hazard of a hopper fire (with proper draft). A DV can be installed with a baro too but it's not standard practice. If I had to do it again I would go with the PV to keep the noise to a minimum but I like the design of the DV and Baro setup best.

Thanks guys , I appreciate your advice. Its something for me to really think about. I also see that the harmon stoker has a DV with the pipe inside the outer pipe which brings in outside air for combustion. This actually looks pretty good, seems safer against possible co leaks and warms incomming air while cooling exhaust gas. What do you think of this setup?

A power venter uses more electricty becuase it's motor is larger. They are a generic unit that get's adujsted to fit your need. A direct vent if purpose built for exactly what it needs to do, thus not being over sized and tuned down.

I'm wondering if some direct venters are less noisy than others. A power venter is not specially quiet. I'd think sometimes a smaller motor in the house could be quieter than a larger one just outside. Either way, the best way is a chimney. If there's any way possible, get one.

I have never actually seen a power venter. The direct vent I had on my stove was very quiet. The blower motor was much louder than the direct vent. Of couse it was a larger motor and fan also. The first time I did fire the stove after connecting to the chimney though, there was a real difference in the noise level.